Apparatus for reducing scale formation



July 24, 1951 c. H. VAN TOORN 2,561,762

APPARATUS FOR REDUCING SCALE FORMATION Filed Oct. 15, 1949 A N T 3* M 9 8 Q I V l w 3 m/ vi/v Toe Patented July 24, 1951 APPARATUS FOR REDUCING SCALE FORMATION Cornelis Hendrik van Too'rn, Til, Netherlands, assignor to N. V. Koninkliika Metaa'lwarenfabrieken v. h. .I. N. Daalderbp 8: zoh'en, 'Tie'l,

Netherlands Application October 15, lc iaiserialjn 121,583 In the Netherlands October-"29, ms

3 Claims. (Cl- 259- -72) Several proposals have been made :!or preventing the forming of incrustation in a chemical or electrolytic way. Such arrangements are however "so extensive, that "they can practically only be considered for steam boilers of high capacity. Moreover these installations are so complicated and expensive in the upkeep, that the same are practically not practised. Often one is content for sealing the incrustation from time to time, this being-especially in water tube boilers-very difficult and expensive.

For cooking-and heating apparatus of less capacity as geysers or electric boilers, which are very sensitive to the forming of incrustation there exists practically no protection against combating the forming of this troublesome incrustation in a suitable manner.

The object of the invention consists in providing an apparatus for preventing suitably the forming of incrustation in all heating apparatus, wherein water is brought at a high temperature. For this purpose watervibrations are excited with a low frequency of e. g. -90 cycles per second. These vibrations may be generated in any manner but it is practical to use for this purpose a membrane excited by an electromagnet connected to a normal mainsfrequency of 50-450 cycles per second.

Such an electromagnetically excited vibrating membrane has Still another advantage that will appear from the following description, in which in view of the annexed drawing some forms of execution according to the invention are elucidated. Herein shows:

Fig. 1 a scheme of a vibrating system combined with a protection against excess pressure in the boiler;

Fig. 2 a scheme of a vibration system combined with another protection against excess pressure in the boiler.

In Fig. 1 the boiler is indicated with I; the membrane 2 is watertightly mounted against the innerwall e. g. the bottom and is brought into vibration by an electromagnet with a U- or M- shaped core 4 the winding 5 of which is connected to the terminals 3 of an alternating mains with the normal mainsfrequency of 50-60 cycles per second.

In the practice it has appeared that the deposit of incrustation is obviated practically completely by the excited vibrations; so the tinned inner surface of an electrical boiler rests completely uncovered below the water level, whilst above the water level a slight deposit takes place.

The anti-incrustation arrangement applied to boiler may suitably be combined with an excess- 'pressure protection. 'For this purpose normally an automatic device for overpressure is used consisting in an elliptical metal 'tube, in which two spring contacts upon each other, so that an electric circuit is closed causing the cutting 01f of the heating body.

In the arrangement of Fig. 1 this overpressureprotection takes place as follows:

Upon one of the legs of the iron core 4 an insulated contact I is mounted cooperating with an earthed contact 6 upon the membrane 2. Under normal working pressures the membrane 2 has the possibility to vibrate freely with the mainsfrequency, the contacts 6 and 'l are separated. When overpressure appears, the membrane 2 is pressed downwardly so far, that the contacts 6 and 1 will touch each other and a circuit is closed: null-terminal 3-upper knife switch l0 -membrane 2contact 6-contact T-cut ofi coil lower knife switch l0R terminal 3, The excited coil 8 draws switch out of the locking catch 9, after which the spring actuated knives are cut oil and the working current for the heating body II is out off. During this action the circuit for the vibration magnet rests closed also after the cutting off of the heating elements.

In the scheme according to Fig. 2 the membrane 2 inside the boiler l is brought into vibration by an electromagnet with U-shaped core 4 the coil 5 of which is connected to the secondary coil H of a combined transformer relay the primary coil l3 of which is connected via the switch III to the mains terminals (50-60 cycles per second). The core I! of the relay is M-shaped and both coils are preferably placed upon the middle leg. The spring actuated armature i6 is withdrawn in the normal working position because a current of suificient highness runs through the secondary coil I4 and the magnet coil 5. Consequently the contacts l5 are opened and the heating body II is cut in.

By the increasing of the pressure in the boiler I the membrane is further pressed down, whilst it is still vibrating, so that the reluctance of the coil increases continually and the secondary current, flowing through the coils 5 and I4, falls gradually. At a predetermined value of this current the armature l6 attracted, the contacts l5 are separated and the heating body I l is cut off.

It is clear that in the described connections different variations may be made without falling beyond the frame of the invention.

What I claim is:

1. Apparatus for reducing scale formation upon the inner surface of a heated hollow vessel containing therein a liquid, including a flexible membrane formed of paramagnetic material, forming a portion of the lower wall of said vessel, and

having one side thereof in contact with saidliquid, an electromagnet so located as to present at least one pole piece thereof closely adjacent said membrane, and means for exciting said electromagnet by alternating current of a frequencyat which said membrane is capable of oscillation.

2. Apparatus according to claim 1, in whichsaid membrane also functions as a pressure-actuated heat control, there being provided a fixed contact upon said electromagnet and almovable contact upon said membrane, so juxtaposed that excess pressure within said vessel will flex said" membrane and will close said contacts together, and relay means whereby said closure cuts oil the supply of heat to said vessel. H

3. Apparatus according to claim 1, wherein the vessel is electrically heated and the exciting means for said magnet include a transformerrelay having a primary connected to said alter- 1 Number '4 hating current and a secondary connected to said magnet, an armature magnetically adjacent the core of the transformer, so biased as to move to and from the transformer in accordance with current flow in said secondary, and bearing thereupon a first contact, and a second fixed contact cooperative with the armature contact, whereby REFERENCES CITED The following references are of record in the file 0! this patent:

UNITED STATES PATENTS Name Date 2,246,165 Dawihl June 17, 1941 2,376,221 Baker May 15, 19 5 

